Thanks Per that fixed it and now I get all my location data working nicely with cgps.

Alas, too soon I spoke Today I decided to rebuild the Raspberry Pi (don't ask!) and the above steps failed. I then remembered that I had previously tried something else from that link - delorian's hint that the socket needed deleting via:

sudo systemctl stop gpsd.socket
sudo systemctl disable gpsd.socket

Ah, now looking at syslog I can see gpsd is starting correctly and, yes indeed, cgps works!